The present invention relates to a manipulator, and in particular, to a manipulator being suitable for use in medical applications.
The manipulators relating to the conventional arts are shown, for example, in U.S. Pat. No. 5,797,900 (Patent Document 1) and U.S. Pat. No. 6,394,998 (Patent Document 2). The manipulator for medical application described in Patent Document 1, uses wires for moving a wrist joint. The position of an actuator, which drives a surgical instrument locating at the tip of the manipulator, is controlled depending on changes in route lengths of the wires. Namely, since the route lengths of the wire change on an inside and an outside of the joint when a first joint is moved on the actuator side, then with using the wires for moving a second joint on the anti-actuator side, also drives the first joint. Also with the Patent Document 2, a joint at a tip portion of a manipulator for medical application, and also a surgical tool provided at a further tip portion of this joint, as well, are rotationally driven or opened/closed by using wires.
For the instruments or tools located at the tip portion of the manipulators for the medical application, there is a requirement that they be small size in, and have plural number of degrees of freedom. In each of the Patent Documents mentioned above, driving force is transmitted through the wire from the actuator to the surgical instrument or tool. However, with such a configuration in which the opening/closing of the manipulator or the surgical tool is driven using the wires, the routes of the wires are changed when an angle of the joint is varied, and there is a risk that the joint cannot perform an oscillating or swinging operation. For dissolving such the drawback, with the Patent Document 1, the joint angle at the tip portion side is controlled by using the driving force due to the change in the route lengths of the wires. For this reason, there is a necessity of controlling a position of a motor, which builds up the actuator.
Also, with the surgical tools described in the Patent Document 2, cooperative control is necessary for the actuators themselves. However, if the cooperative control cannot be done well, tension is applied on the wires too much more than necessity, and there is a possibility that the lifetime of the wires are shortened.